Field: springs, in particular springs used in shoes. It is common in human footwear to have a sole material which compresses to absorb impact energy when the mass of the user is transferred to the shoe during each foot strike. Energy is stored in the compression of the sole and then released back as a vertical force on the bottom of the user's foot. The force required to compress the sole must be high enough to decelerate the mass of the user while walking and/or running. Due to the low travel of this “suspension system”, the bounce frequency of a conventional spring will be higher than the natural frequency of the user's walking or running gait. This causes the energy to be returned at a higher frequency than is desirable. A conventional shoe-sole spring will return the stored energy too early in the foot stride. This does not apply a significant portion of the stored energy to the forward motion of the user. A large number of spring shoe designs are known such as in Illustrato U.S. Pat. No. 4,894,934; Chung U.S. Pat. No. 6,553,692; Illustrato U.S. Pat. No. 4,638,575; Vorderer U.S. Pat. No. 4,943,737; and Meschan U.S. Pat. No. 6,996,924 and it is proposed to provide an improvement over these designs of spring shoes.